Take radiation glass tempering furnace as an example:

Generally, the heating time for clear glass (the time the glass remains in the heating furnace) is set at approximately 30 to 50 seconds for each millimeter of glass thickness.

So, for 6-millimeter thick clear glass, the heating time would be calculated as: 6 × 40 seconds, equalling 240 seconds.

However, the setting of the heating time can vary depending on specific factors. Differences in the area of individual glass pieces and the number of pieces placed in each load can significantly influence the heating time. Therefore, it's necessary to make suitable adjustments during operation, in line with the actual conditions.